The present invention relates generally to methods for descaling devices or components made from metals, and in particular, metallic stents. The methods are particularly directed to the descaling of medical devices made of titanium, stainless steel, tungsten, nickel-titanium, tantalum, cobalt-chromium-tungsten, or cobalt-chromium. While the devices and components to which the present methods are applicable are described mainly as stents, in particular intravascular stents, the invention is not limited to such medical products or stents. For example, the methods may be applied to descale metallic automotive or aerospace structural components.
Stents are generally tube-shaped intravascular devices placed within a blood vessel to maintain the potency of the vessel and, in some cases, to reduce the development of restenosis. The stents may be formed in a variety of configurations which are typically expandable since they are delivered in a compressed form to the desired site. Such a configuration may be a helically wound wire, wire mesh, weaved wire, serpentine stent, or a chain of rings. The walls of stents are typically perforated in a framework design of wire-like connected elements or struts or in a weave design of cross-threaded wire. Some stents are made of more than one material. The stent may be, for example, a sandwich of metals having outer layers of a biocompatible material, such as stainless steel, with an inner layer providing the radiopacity to the stent needed for tracking by imaging devices during placement. A stent made of such material may be, for example, a thin layer of titanium between two layers of stainless steel. In forming such stents from metal, a roughened outer surface of the stent may result from the manufacturing process. It is desirable for the surface of the stent to be smooth so that it can be easily inserted and traversed with low friction through the blood vessels toward the site of implantation. A rough outer surface may not only cause increased frictional obstruction, but may also damage the lining of the vessel wall during insertion. Furthermore, smooth surfaces decrease the probability of thrombogenesis and corrosion.
Since the processing to form metallic stents often results in a product initially having undesirable burrs, sharp ends or debris and slag material from melting the metal during processing, as a first order treatment of the product, descaling of the surface is required in preparation of further surface treatment such as electropolishing.
The present invention provides methods for descaling metallic devices and components, in particular, metallic medical stents.